Portable Tube DAC: Need recommendation

[alexfrenchi]

Hi guy’s,

Looking for some recommendation upon which tubes to get for the build of a portable DAC player that I am building for myself. I will be using it with high impedance headphone's (110ohm), Audeze LCD3

It will be powered by battery, so I can carry it around with me. There will be small movements, I hope this doesnt not inflige in audio quality (or in hearing a sinus noise or some sort, each time I move).

Thank's for your inputs!

If you could add pro's/con's on the model you suggest me.

 

[MarcelvdG]

What do you mean by tube DAC? Does everything have to be done by tubes, or everything that's analogue or mixed signal, or are you thinking about a solid-state DAC with one tube buffer behind it?
Tubes from the D series, such as the DL96, were made for portable equipment and can work with a single 1.5 V cell for the filament supply, see DL96 @ The Valve Museum

 

[alexfrenchi]

Yes, looking into using tubes instead of common transistors. Looking forsomething relatively high-end with a wide spectrum. I heard of other tubes suchas the 6J1 and the NOS 6AK5W, if any of you guy’s have tried those or similarmodels ? The NOS61K5W seems the best so far in terms of sound quality, but requires more powerand all that will be working on battery.

Any tip’sfor my project are the most welcome, being new to this kind of build.

 

[pcan]

If you want full-tube amplification, it will be comparatively heawy and bulky. I have built a DAF96 + DL91 SE amplifier last year and it works well, even as small speaker amplifier, but it is not a device you may want to fit in your pocket. The issue is the output transformer. They can't be too small. At first, I used DL96 tubes as output, but I was unable to find a Hi-Fi quality output transformer at reasonable price, and the ones I tried had severely limited low frequency response. I switched to the beefier DL91 output tube because it does work with regular 5K transformers. My amplfier does have a standard mains power supply, but it could work with a NiCd battery for filament supply and a stack of 9V cells for B+. Directly heated subminiature tubes will also fit this application, check out other threads in this forums.

 

[MarcelvdG]

Between 2013 and 2016 I built a tube DAC that uses tubes for the real digital to analog conversion. Digital signal processing is done by integrated circuits, everything after that by tubes, including the crystal oscillator, clock buffers and voltage reference. It is big, heavy and draws about 60 W of power.

I assume you just want to make the headphone amplifier with tubes. There are tubes meant for driving earphones from a battery supply, namely old hearing aid tubes like the DL64, but they won't help you much: they are meant for quite high load impedances, so you get the transformer problem pcan ran into.

 

[lcsaszar]

Alexfrenchi: you probably want to build the analog part with tubes, including the I/V converter and the headphones driver. I recommend visiting Lampizator's site. As for the power supply, you can run the tube heating from 6V batteries, with a suitable charging circuit. The anode voltage is more difficult. Here an SMPS could create some 150V in small size. I would use Lundahl transformer after the DAC, loaded with a resistor, then a double triode per channel. One half as common grid, the other half as cathode follower, driving the headphones. Coupling capacitors will add to the size, it will not be a pocket DAC.

 

[jazbo8]

Moved to Tubes forum.

 

[jazbo8]

Unless you know how to build a tube DAC yourself, you will end up integrating an existing USB DAC with a tube preamp/HPA...

Something like this: Taga Harmony THA-200 Vacuum Tube Headphone DAC/Amplifier

or Android phones and USB DACs

 

[JPS64]

Why not hybrid? 1AD4 + Mosfet; Lithium battery + Charger + Gauge + Booster + LDO´s; UAC2 receiver and DAC (AKM/ESS/TI) as COTS: OLED, µC (with MMI); and why not aptX receiver (chinese stamps)?

Or like Pete´s Nutube, using Korg 6P1?

Note: microphonis could be a problem!

1AD4 +Mosfet example attached (in the pipeline: breadboard tested).

JS

 

[kazap]

Subminature tubes offer a battery powered pocket potential headphone amp design:

Combine it with a TDA1357 based DAC on a Raspberry Pi and a big pocket for some sweet sound.

An externally hosted image should be here but it was not working when we last tested it.

With the above get rid of the RCA and USB sockets etc to miniaturise and use an SD card for music files.
Use Lithium batteries for compactness - just need a micro-USB socket in the case for recharge. Make the case from aluminium so it warms you up but with a perspex window for coolness and a touch screen on top:

 

[alexfrenchi]

I will tryto get a hold of some ESS Sabre 9018 and couple that with two tubes.

Subminiature tube make’s me feel septic about sound quality, have any of you tried out the Raytheon ?

Otherwise,was thinking to go for some bigger tubes (solid low-end with serious audio quality).
Coupled with some beefed up battery.

Any recommendation for beefier portable tube’s ?

@Kazap, are those the raytheon (6418) tubes. What did you think of them ?
PS: Those guy's also use it: ELEKIT TU-HP03 | Vacuum Tube Hybrid Portable Headphone Amplifier >> getAudio

 

[Lingwendil]

Subminiature tubes are usually pretty good, and some like the russian 6N16B-EV rival the 6SN7 in linearity, but they draw a bit too much heater current to be practical in a portable/battery power setup. If a power brick is acceptable for you, there are a ton of schematics that you can use.

 

[alexfrenchi]

Would having tubes near a bluetooth antenna cause some buzzy noise ?

In terms of spectral bandwidth, a miniature 6N16B-EV rival a bigger 6SN7 ? this is for a headphone use. I’m an audio engineer, I like linearity

Something I notice on some high-end headphone amps, they usually use 4 tubes 2 per channel.

In terms of power consumption, a 6SN7 will be a battery drainer compared to a miniature tube ? or it’s pretty much the same ?

Thanks for your expertise guy’s! Loving it

 

[alexfrenchi]

@Lingwendil Could you share some schematics, especially high-quality/legit one's

PS: If you shake your tube amp, does it make noise ? Asking, as my project wll be for a portable unite in my pocket/belt. So lots of moving around.

Thanks

 

[Lingwendil]

Well, it depends on how you intend to implement the DAC. current or voltage out, and what types of gear you intend to drive. Voltage out into headphones is simple, current out into balanced gear is a bit trickier and still doable.

Are you stuck on the idea of battery power, or will a power brick work? Personally I don't think battery power will be feasible with most tubes unless you really know your way around battery tubes already. A HV boost converter off of a laptop power brick will work well, and if around 1/2w output per channel will work a full push-pull amplifier is possible, but you will at least need a pair of transformers. Altenatively, you could use the tubes for voltage amplification only, and run into a solid state buffer stage. Many options.

 

[alexfrenchi]

I’ll be using a ESS9018 DAC chipset, Ihave to take a look at the doc but I believe it is voltage output. Current has better sound quality ?

The idea of using transformers on aportable (battery) device is a big no no… Those guy’s seem to be running theirs without transformers ? ELEKIT TU-HP03 | Vacuum Tube Hybrid Portable Headphone Amplifier >> getAudio

Using battery for audio quality is a big GAIN (very good & rapid current/voltage quality). Using tubes for voltage amplification doesn’t seem like a win / win.

 

[stocktrader200]

iphone with a tube amplifier and mild bass EQ will beat virtually all DAC's
-100db jitter
112 db dynamic range
104 db s/n 0.002 Thd mostly 2nd harmonic
battery powered as well.
seems capable of 24bit / 96khz flac / DSD files as well with onkyo music app

 

[stocktrader200]

Kazap, great job on the perfboard with 2 tubes and 9v Battery

 

[alexfrenchi]

ES9018 USB DAC - Hi-Resolution System 
I found a guy on the net who build a tube dac around the same chipset I’m going to be using (ESS9018). How can I get around from using big juicy transformers ? My main challenge at the moment.

 

[Lingwendil]

Hard not to unless you go to a hybrid scheme with a solid state output stage really.